Open Spaces

Pintail and wigeon ducks on the move at Bald Knob National Wildlife Refuge in northeast Arkansas. Photo credit: Jim Daniel.

A 2005 newspaper article gave Dr. James Bednarz the idea to look for a possible link between climate change and duck migration.

In the article, someone suggested climate change was already reducing duck hunting opportunities in Arkansas, a state known for its premier waterfowl hunting.

“I thought it was pretty farfetched,” Bednarz recalled recently.

But the hypothesis presented an interesting research project. After diving into 50 years worth of duck data, Bednarz, a professor of Wildlife Ecology at Arkansas State University in Jonesboro, says he’s now convinced climate change -- including warmer temperatures, more ice-free days and changes in precipitation -- is causing fewer ducks to migrate south for the winter.

“The analysis definitely demonstrates that change is happening right now,” Bednarz said. “If [climate change] continues, waterfowl hunting in places where we’ve traditionally done it will seriously diminish. I think it will be a big cost to our heritage and our wildlife.”

In an unpublished paper, Bednarz, a colleague, and a graduate student studied duck data collected between 1955 to 2004 through the Midwinter Waterfowl Inventory conducted by the U.S. Fish and Wildlife Service and state wildlife agencies, and the Christmas Bird Count led by the National Audubon Society. The team juxtaposed those snapshot winter numbers against dozens of variables: weather data from NOAA; crop production data, to estimate the availability of food and habitat for ducks; duck hunting effort and success; and estimated breeding populations for the Mississippi Flyway, a bird migration route that generally follows the Mississippi River.

Warmer winters equated to more ducks in states like Minnesota, Illinois, Iowa and Ohio, and fewer ducks in Arkansas, Alabama, Louisiana, Mississippi and Tennessee.

For dabbler ducks -- those that eat food just below the surface of a pond or wetland -- the climate variables showed a 96 percent probability of explaining the changes in duck abundance in various locations along the flyway. For mallard ducks, the most popular species among hunters, the probability was 99 percent.

“That’s just incredible,” Bednarz said.

Arkansas, along the Mississippi Flyway, is a premier state for waterfowl hunting. Fifty years worth of duck data indicate climate change may be already reducing duck hunting opportunities. Photo credit: USFWS.

Hunting success from the previous year was the only other factor that showed even minor probability of predicting the changes in duck numbers within the flyway.

Bednarz and his colleagues cite other research to help explain why fewer ducks may fly south for the winter in a changing climate. Ducks need ice-free wetlands and plenty of food – two requirements that are historically lacking during the winter in states like Michigan and Wisconsin in the northern section of the Mississippi Flyway. Warmer winters mean ducks would not need to fly as far south as they have historically to meet their needs.

Ducks Unlimited Chief Scientist Dale Humburg is more reserved about drawing strong conclusions regarding dynamic variables that affect duck numbers. But he is convinced that waterfowl and their habitat -- already affected by wetlands loss and alteration -- could see exaggerated effects of changing climate.

“It’s difficult to predict local or regional impacts in the absence of down-scaled [climate] models and the considerable variation in annual duck distribution, habitat conditions and weather,” Humburg says.

In a 2010 white paper co-written with Dawn Browne, manager of conservation programs for Ducks Unlimited, Humburg expressed concern that warmer and drier conditions in Arkansas and other Mississippi Alluvial Valley states could lead to lower stream flows and groundwater levels, negatively impacting wetlands and waterfowl.

Humburg and Bednarz agree that one important solution is to protect additional waterfowl habitat, particularly their breeding grounds, where it is now and where it will need to be in the future if waterfowl populations are to endure.

“We need to be able to anticipate changes in bird distribution and make sure the habitat is available to support them” Humburg said.